Production of metal-impregnated porous coke materials

ABSTRACT

Metal impregnated porous materials, e.g. magnesium impregnated coke, are produced by immersing pieces of porous material in molten metal and then dumping them into a fluidized bed of granular material to quench them.

United States Patent Layland [4 Apr. 18, 1972 [541 PRODUCTION OF METAL- [56] References Cited IMPREGNATED POROUS COKE M UNI'I ED STATES PATENTS [72] Inventor: Kenneth Frederick Layland, Nechells, Bir- 32: "117/71 R England 2,561,393 7/1951 Marshall [73] Assignee: Foseco International Limited, Birmingham, 3,053,704 9/1962 Munday ..117/DIG. 6

England FOREIGN PATENTS OR APPLICATIONS [22] Filed: 1970 1 381824 11 1964 r 117 1 [21] pp No: 19,123 rance /D G. 6

Primary ExaminerAlfred L. Leavitt [30] Foreign Application Priority Data Assistant Examiner-J. R. Batten, Jr.

Mar. 19, 1969 Great Britain ..l4,538/69 Hubbard 52 us. c1 ..ll7/l6, 75/53, 75/58, [57] ABSTRACT 1 /6 117/71 114 Metal impregnated porous materials, e.g. magnesium im- 1 17/ l 160 1 1 10 pregnated coke, are produced by immersing pieces of porous [5 l] Int. Cl ...B44Cl 1/44, C23C I/IO, C23f17/00 material in molten metal and then dumping them into a [58] Field of Search ..1 17/1 19.2, DIG. 6,114 R, 114A,

117/114 B, 114 C, 71 R, DIG. 11, 16, 69

fluidized bed of granular material to quench them.

i 9 Claims, N0 Drawings PRODUCTION OF METAL-IMPREGNATED POROUS COKE MATERIALS This invention relates to the production of metal-im pregnated porous materials. It is of particular value in connection with the production of metal impregnated coke, and particularly magnesium impregnated coke, and will be described with particular reference thereto. However the invention is of wider applicability in that it may be employed for the production of materials of the said type irrespective of the porous material and metal to be used.

It is a known technique in the treatment of molten ferrous metals to produce nodular iron to add to the molten metal a portion of magnesium. Nodular iron is sometimes referred to as spheroidal graphite iron, or as ductile iron. Further, magnesium, and the alkali metals, are useful additives for the purpose of converting any dissolved iron oxides or finely dispersed silicates in the molten metal into insoluble magnesium or alkali metal oxides and silicates.

Because of the practical difficulties of using such metals as magnesium and sodium, due to volatilization or burning of the additive in use and the violence of the reaction which takes place, it has been proposed to employ as the additive for the molten metal a porous carrier material such as porous coke, carbon or graphite which has been impregnated with the desired metal (usually magnesium or an alkali metal). The porosity of the carrier may be, for example, up to 50 percent, i.e. 50 percent of the total volume of the carrier is made up of pores.

The production of such an additive has hitherto been effected by plunging the porous carrier material into a molten bath of the desired metal (e.g. magnesium or alkali metal) so that the pores become filled, or at least partially filled, with the metal, and then solidifying the molten metal in the pores by chilling the impregnated porous body obtained. The chilling, or quenching, operation is effected by plunging the hot impregnated material into an oil bath.

This method has serious practical disadvantages among which are that there is danger of the hot impregnated material igniting the oil bath, there is usually a very considerable production of smoke from the burning oil, and there is a need from time to time to clean the oil of the bath since it tends to become heavily contaminated by dross and carrier material (e.g. burned coke) which collects as a sludge. Moreover it is customary to remove the quenched material from the oil bath while the said material is still hot. There is thus a subsequent volatilization and/or burning of the oil with consequential hazards and inconveniences.

It is an object of the present invention to provide a novel method for the production of metal impregnated porous carrier materials which avoids the foregoing disadvantages and yields a product of particularly good quality and efficiency.

According to the present invention there is provided a process for the production of a porous carrier material having a metal impregnated into the pores thereof which comprises impregnating pieces of porous carrier material with hot molten metal so that the same enters the pores thereof, and depositing the impregnated product into a fluidized bed of granular material thereby to quench it.

There are basically two variations of the technique which may be employed, one in which .the fluidized condition of the bed is maintained during the quenching steps and the other in which, after the deposition of the impregnated material into the bed, the fluidization of the bed is stopped. In this latter case the impregnated metal is simply enveloped by the solid material of the bed and the quenching operation is rapidly effected. In the former case the quenching is effectively achieved by the gas flow (usually air flow) which keeps the bed in fluidized condition: that gas flow efficiently cools the impregnated material and it has been found that, somewhat surprisingly, even when the porous carrier is. coke and the metal is magnesium, there is very little oxidation of either material resulting from an air flow.

A principal advantage of the use of a fluidized bed as a quenching medium is that it tends to distribute the impregnated material according to its effective density. Thus fully impregnated pieces of porous carrier, due to their metal content, tend to be heavier and to sink in the bed, while any pieces of porous carrier which have not become impregnated or are only very lightly impregnated (and which are therefore unsatisfactory or less satisfactory) tend to form a dross floating on the surface of the bed. Hence by skimming this dross a final product, recovered from the lower ranges of the bed, of high average quality is obtained.

As noted above the porous material is preferably coke but other porous materials may be employed according to the use to which the final metal-impregnated material is to be put. The term pieces is used herein to cover pieces of widely varying size, for example from granules to lumps. Coke pieces for impregnation may vary from 6mm to 15 cm in mean diameter.

The metal may be any such as may be required in the final product but for use in the production of additives for molten ferrous metal, the impregnated metal is preferably magnesium or an alkali metal such as sodium, potassium or lithium. Other metals, e.g. aluminum or copper may be used for special purposes.

In a modification of the invention the porous carrier may be impregnated with more than one material, including a metal, again to produce products of value for special purposes.

The fluidized bed may be-made of any granular particulate material, preferably non-porous. A very suitable material is fine dry sand. It is preferable to select a material which has a density lying between the density of the porous carrier material and a fully metal impregnated carrier material.

It is possible, using the method of the invention, to produce metal-impregnated porous materials, the pieces of which bear on outer coating of fusible material, by including such fusible material, in granular fonn, in the fluidized bed itself. Such a treatment may be employed, for example to protect the pieces of metal-impregnated porous material, or to produce compound treatment products comprising a metal-impregnated porous material surrounded by a fusible treatment casing.

Two particularly valuable coatings are to be noted, both of which are applied to magnesium-impregnated coke or like material for molten ferrous metal treatment. First, fluxing materials such as alkali and alkaline earth halides e.g. sodium fluoride or calcium fluoride, or complex fluorides such as cryolite, may be used either instead of or together with materials such as silica sand in the fluidized bed to form a coating on the magnesium impregnated coke. When the magnesium impregnated coke is used to treat molten iron the halide coating materials produce a fluxing efiect on the resulting dross.

Second, rare earth halides may be used in asimilar way to the halides referred to above to form a coating on magnesium impregnated coke. During the treatment of molten iron the magnesium vapour produced from the magnesium impregnated coke reduces the halides to the metal, for example cerium fluoride may be reduced to cerium metal, and the metal acts to counteract the effect of elements such as bismuth or titanium, which may be present in the iron and which would normally prevent effective conversion of the graphite in the iron to nodular or spheroidal form.

It is to be understood that in addition to the specific metal impregnants noted above, alloys can be used as impregnants, particularly alloys of the metals noted above or containing one or more such metals.

1 claim:

1. In the production of a porous coke carrier material having a metal selected from the group consisting of magnesium, sodium, potassium and lithium impregnated into the pores thereof by impregnating pieces of porous coke carrier material with hot molten metal so that the same enters the pores thereof and thereafter quenching the impregnated product to solidify the molten metal, the improvement comprising depositing the impregnated product into a fluidized bed with air as the fluidizing medium of a granular particulate material to quench the impregnated product.

2. A process according to claim 1 wherein the fluidization of the bed is maintained substantially throughout the quenching step.

3. A process according to claim 1 wherein the fluidized bed consists substantially of fine dry sand.

4. A process according to claim 1 wherein the fluidized bed contains a granular fusible material which forms a coating on the pieces of porous material.

5. A process according to claim 4 wherein the granular fusible material is a member selected from the group consisting of alkali and alkaline earth metal halides and complex halides.

6. A process according to claim 4 wherein the granular fusible material is a rare earth metal halide.

7. A process according to claim 1 wherein the metal for impregnating is an alloy containing at least one metal selected from the group consisting of magnesium, sodium, potassium and lithium.

8. A process according to claim 1 wherein the particulate material has a density between the density of the porous coke carrier and the fully impregnated product.

9. A process according to claim 1 wherein the fluidized bed presents a top surface and lower ranges which includes skimming the lightly impregnated material from the surface of the bed and recovering the quenched impregnated product from the lower ranges of the bed. 

2. A process according to claim 1 wherein the fluidization of the bed is maintained substantially throughout the quenching step.
 3. A process according to claim 1 wherein the fluidized bed consists substantially of fine dry sand.
 4. A process according to claim 1 wherein the fluidized bed contains a granular fusible material which forms a coating on the pieces of porous material.
 5. A process according to claim 4 wherein the granular fusible material is a member selected from the group consisting of alkali and alkaline earth metal halides and complex halides.
 6. A process according to claim 4 wherein the granular fusible material is a rare earth metal halide.
 7. A process according to claim 1 wherein the metal for impregnating is an alloy containing at least one metal selected from the group consisting of magnesium, sodium, potassium and lithium.
 8. A process according to claim 1 wherein the particulate material has a density between the density of the porous coke carrier and the fully impregnated product.
 9. A process according to claim 1 wherein the fluidized bed presents a top surface and lower ranges which includes skimming the lightly impregnated material from the surface of the bed and recovering the quenched impregnated product from the lower ranges of the bed. 